1. Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to PDCP-layer algorithms for managing packets sent over a plurality of downlink cells for aggregation.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.
As an example, Multi-Point HSDPA has been recently introduced, in which multiple cells can provide high-speed downlinks within the same carrier frequency to a mobile station, such that the mobile station is capable of aggregating the transmissions from those cells. In one example of a Multi-Point HSDPA system, multiple MAC layer links exist: each serving cell manages its own MAC entity, with respective links to a mobile station that includes a corresponding number of MAC entities, one for each serving cell. In this scheme, it is possible that the packets received at the mobile station over the multiple MAC layer links can skew, or arrive out of order according to their respective sequence numbers. If unchecked, this skew can result in unnecessary retransmissions of packets. Therefore, there is a need for protocols for Multi-Point HSDPA networks capable of addressing this skew in a way that is mindful of the potential skew and can handle it without triggering unneeded retransmissions.